Overview
Despite being a Dwarf Planet, Pluto, named after the Roman god of the Underworld, is still a part of our Solar System. It’s status as a Dwarf Plant makes it even more interesting.
Classification
Pluto is classified as a Dwarf Planet. In our Solar System there are 5 dwarf planets. These planets are small. They are as small as or smaller than some of the moons scattered throughout the solar system.
Size
Pluto is ⅙ the size of Earth or ⅔ the size of Earth’s moon. Pluto’s radius is 715 miles. This is about the same distance as from New York City, New York to Indianapolis, Indiana or ¼ of the distance across the United States.
Rotation
One day on Pluto is 6.38 Earth days and one year is 248 Earth years.
Position
Pluto has a tilt of 57 degrees, so it spins almost on its side. But it’s not as dramatic as Uranus’ tilt.
Like Venus and Uranus, it spins backwards. This means Pluto rotates from east to west.
Pluto’s orbit is elliptical and tilted. Pluto’s orbital is not in line with the other planets. In fact, Pluto orbits down into Neptune’s orbit, around the Sun and outside Neptune’s orbit. Then it goes up through Neptune’s orbit and outside.
Pluto averages 3.7 billion miles from the Sun. It takes 5.5 hours for sunlight to reach Pluto.
Structure
Pluto’s structure is probably a rocky core surrounded by a mantle of ice water. It is hard to tell with only one fly by mission by New Horizons Satellite. Of the planets, Pluto is still very mysterious.
The surface of Pluto is covered in mountains, valleys, plains and craters made out of ice. The mountains can be as tall as 6,500 to 9,800 ft high and are made out of big blocks of ice water that can be cover in frozen methane. The valleys and troughs can be as long as 370 miles. Some of the craters on Pluto can be as large as 162 miles in diameter. There may be some tectonic forces that are resurfacing that cause the mountains and valleys.
Pluto is ⅙ the density of the Moon.
The average temperature is between -375 and -400 degrees F.
The gravity on Pluto is .0066 that of Earth. Anything that landed on Pluto might drift off into space.
Atmosphere
Pluto has a thin atmosphere that expands and contracts. It is made up of molecular nitrogen, and possibly methane and carbon monoxide. When Pluto nears the Sun during its orbit, the surface thaws into gas and the atmosphere expands.
Moons
All of Pluto’s moons are named after Greek mythological underworld beings. Pluto has 5 moons. The largest one, Charon, is half the size of Pluto and orbits 12,200 miles from Pluto. It takes Charon 153 hours to orbit Pluto, about the same time as one day on Pluto. Charon is the only spherical moon. Pluto’s and Charon orbit in more of a binary system than planet and moon. A binary system is when two objects in space, like Pluto and Charon, spin around each other.
Pluto’s other moons are Nix, Hydra, Kerberos, and Styx. They are more irregular in shape, unlike Charon. They are also much smaller at less than 100 miles wide.
Fun Facts
Pluto and Charon always see the same spot of each other as they orbit. This is called tidal locking. This means Charon doesn’t spin around like other moons, but is locked so one side is always facing Pluto.
Pluto is part of the Kuiper Belt that orbits beyond Neptune. Three more dwarf planets are also found in the Kuiper Belt, Makemake, Haumea and Eris.
Other dwarf planets include Ceres, found in the asteroid belt.